Use of high water marks and eyewitness accounts to delineate flooded coastal areas: The case of Storm Johanna (10 March 2008) in Brittany, France

► The use of eye witness accounts, high water marks and topographic survey for flooded zone delineation is for the first time used in a mega and macrotidal environnement, where inundations do not last a longtime. ► The observed data set and specific analysis for the study region provide thus information which may be useful for follow-on coastal flood work in Brittany. ► The study conducted on Beniguet Island shows that the wave overtopping model, based on van der Meer and Jansen (1995), used for designing coastal structures such as breakwaters or jetties, is also useful for natural barriers such as dunes and shingle barriers.